Add the mailing list to the contact page

data/contact.md

@@ -6,6 +6,9 @@ You can easily reach the team via our <a href="https://app.gitter.im/#/room/#swi
 
 ### E-mail
 
+You can also join our <a href="https://mail.strw.leidenuniv.nl/mailman/listinfo/swift-users">mailing list</a>.
+This is a low-traffic, announcement-only list to keep updated on releases and other important changes.
+
 Alternatively, you can contact us using the form below. <br/>
 
 <form action="https://formspree.io/f/xzbqkdyk" method="POST">